Progressbar ne s'affiche pas malgré setVisible(true)

import javafx.concurrent.Task;

public class ProgressTask extends Task<Void> {
    @Override
    protected Void call() throws Exception {
        int count = 100;
        for (int i = 0; i < count; i++) {
            update(i, count);
            task(i, count);
        }
        update(count, count);
        return null;
    }

    private void task(int i, int count) throws Exception {
        Thread.sleep(50);
    }

    private void update(int i, int count) {
        updateProgress(i, count);
        updateMessage("Item " + i + "/" + count);
    }
};

import javafx.application.Application;
import javafx.concurrent.WorkerStateEvent;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ProgressBar;
import javafx.scene.layout.FlowPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class ProgressBarApplication extends Application {

    @Override
    public void start(Stage primaryStage) {
        final Button startButton = new Button("Start");

        final ProgressBar progressBar = new ProgressBar(0);
        progressBar.setMinWidth(250);

        final Label statusLabel = new Label("Non Démarré...");
        statusLabel.setMinWidth(50);

        startButton.setOnAction(actionEvent -> {
                    ProgressTask task = new ProgressTask();

                    startButton.setDisable(true);
                    progressBar.setProgress(0);
                    statusLabel.setText("Démarré !");
                    progressBar.progressProperty().bind(task.progressProperty());
                    statusLabel.textProperty().bind(task.messageProperty());

                    task.addEventHandler(WorkerStateEvent.WORKER_STATE_SUCCEEDED, workerStateEvent -> {
                        statusLabel.textProperty().unbind();
                        progressBar.progressProperty().unbind();
                        statusLabel.setText("Terminé !");
                        progressBar.setProgress(1);
                        startButton.setDisable(false);
                    });

                    new Thread(task).start();
                }
        );

        FlowPane root = new FlowPane();
        root.setPadding(new Insets(10));
        root.setHgap(10);
        root.getChildren().addAll(startButton, progressBar, statusLabel);

        Scene scene = new Scene(root, 450, 50, Color.WHITE);
        primaryStage.setTitle("ProgressBar");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        Application.launch(args);
    }
}